(a) Field of the Invention
This invention generally relates to a bullet that includes weakened grooves that allow the bullet to separate along pre-determined locations upon impact with a target, such as an animal. More particularly, but not by way of limitation, this invention relates to a controlled fragmenting bullet that uses the centrifugal force imposed by firing the bullet through a rifled barrel to enhance the distribution of the bullet fragments through the animal""s body.
(b) Discussion of Known Art
The effectiveness of a particular bullet depends on the type of target and the distance from the gun at which the target is likely to be found. However, in order to maximize the killing ability of a particular bullet, it is well recognized that the use of controlled fragmentation projectiles results in greater damage to an animal as compared to bullets of equal mass and fired with the same velocity (all other factors being equal). The increased killing ability is largely due to the creation of multiple wound paths associated with each of the bullet fragments.
In order to take advantage of the effectiveness of fragmenting bullets, many bullet designers have come up with various configurations that are designed to break apart once the bullet strikes the animal. It is important to note that many fragmenting bullet designs have proven to be ineffective due to uncontrolled fragmentation, meaning complete disintegration of the bullet components upon striking the target. When fired through rifled barrels, the uncontrolled fragmentation is largely caused by the fact that the spinning of the bullet induced by the rifling imposes tremendous centripetal forces on the bullet. The components or materials used to hold the bullet together during travel are often not capable of adequately resisting these forces upon impact, and thus result in the uncontrolled complete disintegration of the bullet and very limited penetration. The forces induced by rifling are significant, since a bullet fired at 3,000 feet per second can achieve a rotational velocity of approximately 3,000 revolutions per second with common degrees of rifling. The centripetal force required to keep the fragments from separating can be calculated from the formula: F=mrxcfx892, where m is the mass of the fragment, r is the radius or distance from the central axis of the bullet to the center of gravity of the fragment, and xcfx89 is the speed of rotation (in radians per unit of time). It is important to note that the term xe2x80x9ccentrifugal forcexe2x80x9d is used herein to refer to the centripetal acceleration on a mass of material.
Accordingly, it will be understood that more aggressive rifling will have a more dramatic effect on the centripetal force than the caliber or size of the bullet, or the mass of the bullet or fragment. However, the important aspect to keep in mind from the above discussion is that the rotation due to rifling transfers a tremendous amount of energy into the bullet, and that this energy is stored in the bullet due to the rotation of the bullet. Furthermore, it is important to note that this rotational energy is not lost as quickly as the energy or momentum associated with the linear velocity of the bullet. The energy associated with linear velocity is lost rather quickly due to the aerodynamic forces (drag and turbulence effects) that are encountered by the bullet as it travels though the air. The rotational energy of the bullet, however, is largely preserved throughout the trajectory. The preservation of the rotational velocity and energy is largely due to the fact that the skin friction drag encountered in the direction of rotation, while the bullet rotates, is very small as compared to the aerodynamic forces encountered by the front of the bullet as it moves through air.
A review of known devices reveals that there are few bullets that take advantage of centripetal forces and the availability of energy stored in the bullet""s rotation.
It has been discovered that the problems left unanswered by known art can be solved by providing a bullet that includes:
(1) a generally cylindrical body having a nose, a mid-portion and a heel, the body having an aperture that starts at the nose, extends past the mid-portion of the bullet and ends near the heel of the bullet; the aperture also includes at least two scored areas along the sides of the aperture and extending along at least some or all of the aperture; and
(2) a scored area along the heel portion of the bullet, the scored area along the heel terminating at a location that aligns with the scored area along the sides of the aperture in the bullet.
It is contemplated that the aperture in the bullet may be round with at least two or more scored grooves that extend along part of the entire length of the aperture. However, it is contemplated that the aperture, which is usually round, may be rectangular, square, triangular, slit shaped, parallelogram, diamond shaped, polygonal or other shape that causes deliberate stress points or breaking areas in the aperture, in order to induce controlled fragmentation of the bullet upon impact.
The scored grooves on the heel or rear end of the bullet will line up with the scored grooves along the inside of the aperture in the bullet. It has been discovered that by aligning scored grooves along the heel of the bullet with the corresponding scored areas or grooves along the sides of the aperture in the bullet, a controlled, deliberately fragmenting bullet that takes advantage of the momentum due to the rotation from rifling can be achieved. In operation, the bullet achieves a high rate of rotation from the rifling in the barrel of the gun. Then, as the bullet strikes a target, it begins to split along the scored grooves, or deliberate stress points, on the sides of the aperture. The bullet""s rotation will then cause the individual fragments to move away from the bullet""s line of travel. The scoring along the length of the bullet""s aperture will force the separation to continue at the grooves or weakened areas on the heel of the bullet. The result is the controlled and deliberate separation of multiple fragments, with none of the fragments moving along the original line of travel of the bullet. This will result in multiple wound paths, each caused by a fragment that takes advantage of both the rotational momentum and the linear momentum of the bullet.
While the above and other advantages and results of the present invention will become apparent to those skilled in the art from the following detailed description and accompanying drawings, showing the contemplated novel construction, combinations and elements as herein described, and more particularly defined by the appended claims, it should be clearly understood that any changes in the precise embodiments of the herein disclosed invention are included within the scope of the claims, except insofar as they may be precluded by the prior art.